The present invention relates to a device and method for inspecting stripe electrode patterns formed on a substrate, so as to detect defects in the patterns.
Conventionally, in a large-scale liquid crystal display element capable of displaying high-definition characters and images, a plurality of transparent electrodes are formed in a stripe form so that fine-pitched electrode patterns are provided on one of two transparent substrates in pair composing the liquid crystal display element.
In a process of fabrication of the transparent substrate with such transparent electrodes, used as a common technique to detect defects in the electrode patterns are {circumflex over (1)} a method disclosed in the Japanese Publication for Laid-Open Patent Application No. 333357/1993 (Tokukaihei 5-333357 [Issue Date: Dec. 17, 1993]), and {circumflex over (2)} a method disclosed in the Japanese Publication for Laid-Open Patent Application No. 230188/1990 (Tokukaihei 2-230188 [Issue Date: Sep. 12, 1990 ]).
In the case where the method {circumflex over (1)} is adopted, used is an inspection device 101 provided with, as shown in FIG. 6, a first voltage inspection terminal 102, a voltage application terminal 103, a second voltage inspection terminal 104, an inspecting voltage application circuit 105, a defect detection circuit 106, and a short-circuiting/wire breakage memory circuit 107. The voltage application terminal 103 is connected with the inspection voltage application circuit 105, while the first and second voltage inspection terminals 102 and 104 are connected with the defect detection circuit 106. The defect detection circuit 106 is connected with the short-circuiting/wire breakage memory circuit 107, and is also earthed.
The plurality of transparent electrodes (electrode patterns) 121 in a stripe form are formed on the transparent substrate 120 as described above, and the voltage application terminal 103 is in contact with an end of one transparent electrode 121 a thereamong, while the first voltage inspection terminal 102 is in contact with the other end of the transparent electrode 121a. Likewise, the second voltage inspection terminal 104 is in contact with an end of a transparent electrode 121b adjacent to the transparent electrode 121a, the end being on the first voltage inspection terminal 102 side. If the defect detection circuit 106 detects no conduction between the voltage application terminal 103 and the first voltage inspection terminal 102 upon application of a voltage by the inspection voltage application circuit 105, it follows that the transparent electrode 121a is broken. If the defect detection circuit 106 detects conduction between the voltage application terminal 103 and the second voltage inspection terminal 104, it follows that the transparent electrodes 121a and 121b are short-circuited. The foregoing defect information thus detected is outputted to and stored in the short-circuiting/wire breakage memory circuit 107.
By driving the three terminals, that is, the voltage application terminal 103 and the first and second voltage inspection terminals 102 and 104, in a direction crossing the transparent electrodes 121 in a stripe form so as to scan the transparent electrodes 121, all the transparent electrodes 121 on the transparent substrate 120 are subjected to inspection on presence/absence of wire breakage and short-circuiting.
On the other hand, in the case where the method {circumflex over (2)} is adopted, used is a transparent substrate 122, as shown in FIG. 7, having a common electrode 124 formed at a peripheral part thereof outside to transparent electrodes (electrode patterns) 123 arranged in a stripe form and connected with every other transparent electrode 123. More specifically, the transparent substrate 122 used when the method {circumflex over (2)} is applied is designed so that thereon alternately arranged are transparent electrodes 123a connected with the common electrode 124 and transparent electrodes 123b not connected therewith. Further, as shown in FIG. 7, an inspection device 110 used in this method is designed in the same manner as the inspection device 101 used in application of the method {circumflex over (1)} except that not two voltage detection terminals, but a single voltage inspection terminal 108 is used alone.
The foregoing voltage application terminal 103 is brought into contact with the common electrode 124, while the voltage inspection terminal 108 is brought into contact with an end of one transparent electrode 123 and makes the contact scan in a direction crossing the transparent electrodes 123. In the case of one transparent electrode 123a not connected with the common electrode 124, without short-circuiting, a voltage is not detected from the voltage inspection terminal 108 by the defect detection circuit 106, whereas with short-circuiting, a voltage is detected. Conversely, in the case of one transparent electrode 123b connected with the common electrode 124, without wire breakage, a voltage is detected from the voltage inspection terminal 108 by the defect detection circuit 106, whereas with wire breakage, voltage is not detected.
Therefore, without any irregularity such as wire breakage or short-circuiting in the transparent electrodes 123, some transparent electrodes 123 at which a voltage is detected (voltage-detected transparent electrodes 123) and some transparent electrodes 123 at which a voltage is not detected (voltage-non-detected transparent electrodes 123) appear alternately (voltage is detected from the transparent electrodes 123b connected with the common electrode 124 while voltage is not detected from the transparent electrodes 123b not connected with the common electrode 124). With wire breakage or short-circuiting, however, voltage-detected transparent electrodes 123 or voltage-non-detected transparent electrodes 123 appear successively.
Therefore, such successive appearance of voltage-detected transparent electrodes 123 or voltage-non-detected transparent electrodes 123 is detected by the defect detection circuit 106 as a defect of wire breakage or short-circuiting, and it is, as defect information, outputted to and stored in the short-circuiting/wire breakage memory circuit 107.
The foregoing conventional methods have the following problems, however.
First of all, the transparent electrodes 121 subjected to an inspection by the method {circumflex over (1)} have to be in a complete stripe form. The reason is as follows: since the voltage application terminal 103 and the first and second voltage inspection terminal 102 and 104 are in point contact with ends of the transparent electrodes 121, if the pitch of ends of the transparent electrodes 121 varies somewhere, an adequate electric circuit is not provided, thereby making inspection impossible.
Further, the method {circumflex over (1)} requires high precision in positioning of the terminals and the plurality of transparent electrodes 121 disposed on the transparent substrate 120. In other words, unless the parallelized state of the terminals is set accurately and precisely, the terminals and the transparent electrodes 121 do not form an adequate electric circuit. Likewise, unless the transparent electrodes 121 are disposed at precise and accurate positions on the transparent substrate 120, the parallel state of the terminals has to be set for each inspected transparent substrate 120 independently. To realize such high precision in positioning, a system for high-precision positioning system is needed, thereby bringing about an increase in costs.
Furthermore, the method {circumflex over (1)} is incapable of inspection of electrode patterns designed so that an end of every transparent electrode 121 is connected with the above-described electrode 124. In other words, according to the method {circumflex over (1)}, the voltage application terminal 103 and the first voltage inspection terminal 102 are brought into contact with ends of one transparent electrode 121a on both sides, respectively, and the second voltage inspection terminal 104 is brought into contact with an adjacent transparent electrode 121b, but in the case where the common electrode 124 connected with every transparent electrode 121 is provided on the transparent substrate 120 (not illustrated), voltage is in the same manner applied onto the adjacent transparent electrodes 121a and 121b both via the common electrode 124, upon voltage application by the inspection voltage application circuit 105. Therefore, voltages with the same value are detected from the first and second voltage inspection terminals 102 and 104.
In this case, wire breakage can be detected from the transparent electrode 121a in contact with the voltage application terminal 103 and the first voltage inspection terminal 102, but detection of short-circuiting of the transparent electrode 121b in contact with the second voltage inspection terminal 104 is impossible, since the transparent electrode 121b is electrically connected, via the common electrode 124, with the transparent electrode 121a in contact with the first voltage inspection terminal 102.
Likewise, the method {circumflex over (2)} is incapable of inspection of electrode patterns designed so that an end of every transparent electrode 121 is connected with the above-described electrode 124 (not illustrated). The method {circumflex over (2)} is an electrode pattern inspection method applicable to electrode patterns formed in a stripe form and designed so that every other transparent electrode 123 is connected with the common electrode 124. Therefore, in the case of an electrode pattern inspection method in which an end of every transparent electrode 123 is connected with the common electrode 124, like in the foregoing method {circumflex over (1)}, detection of wire breakage is possible, whereas short-circuiting between adjacent transparent electrodes 123a and 123b is impossible since voltages with a similar value are detected from the adjacent transparent electrodes 123a and 123b. 
An object of the present invention is to provide a device and method for surely inspecting electrode patterns arranged in a stripe form so that an end of every electrode pattern is connected with a common electrode, without being affected by the precision in positioning of the electrode patterns.
To achieve the foregoing object, an electrode pattern inspection device of the present invention is characterized by comprising (1) a current application section for applying constant electric current to an electrode to be inspected that is one of a plurality of electrodes having first ends connected with each other by a common electrode, and second ends opposite to the first ends, and for detecting variation in a voltage generated by the constant current, (2) a voltage detection section for measuring a voltage at an electrode adjacent to the electrode to be inspected, and detecting variation in the voltage, and (3) an earth section for earthing the common electrode.
The foregoing arrangement enables inspection to the electrode patterns arranged so that ends thereof on one side (first ends) are connected with each other by the common electrode, with regard to whether or not each electrode is broken and whether or not each electrode is short-circuited with an adjacent electrode.
Incidentally, in the case where by using a conventional electrode pattern inspection device each electrode is inspected with regard to whether or not it is short-circuited with an adjacent electrode, a voltage is applied to the inspected electrode, and a voltage at the electrode adjacent to the inspected electrode is measured. Then, in the case where the voltage of not zero volt is measured, it is judged that the electrodes are short-circuited.
However, by this method, a plurality of electrode patterns whose ends on one side are connected with each other by a common electrode cannot be inspected. This is because a voltage detected at an electrode adjacent to an inspected electrode is not zero also when the electrodes are not short-circuited, since each electrode is connected with an electrode adjacent thereto via the common electrode.
Conversely, in the foregoing arrangement of the present invention, since the common electrode is earthed by the earth section, the constant current applied to an inspected electrode by the current application section flows into the earth via the earth section, if the electrode pattern has no defect. Therefore, the constant current applied does not flow into an electrode adjacent thereto, and the voltage detected by the voltage detection section is zero. On the other hand, in the case where the electrode inspected is short-circuited with an electrode adjacent thereto, a voltage of not zero is detected by the foregoing voltage detection section. Thus, the use of the electrode pattern inspection device of the present invention enables detection of short-circuiting, which the conventional inspection device is incapable of.
In the case where the inspected electrode is broken, the resistance of the electrode becomes infinite. Therefore, it is possible to find the occurrence of such wire breakage from the voltage detected by the foregoing current application section.
The foregoing electrode pattern inspection device of the present invention is preferably arranged so that (1) the current application section has a current application terminal in contact with an end on the second side of the inspected electrode, (2) the voltage detection section has a voltage detection terminal in contact with the second end of the electrode adjacent to the electrode to be inspected, (3) the earth section has an earth terminal in contact with the common electrode, and (4) the current application terminal and the voltage detection terminal are shaped so as to be in point contact with the electrodes, respectively, while the earth terminal is shaped so as to be in area contact with the common electrode.
According to the foregoing arrangement, the current application terminal for applying constant current and the voltage detection terminal for measuring a voltage in a needle form (for example, in a probe form) so as to be brought into point contact with the transparent electrode. Therefore, each of these terminals is not brought into contact with a plurality of electrodes among the fine-pitched electrodes, thereby ensuring accurate inspection.
Furthermore, since the earth terminal is formed in a shape such that the earth terminal is in area contact with the common electrode and the area in which they are in contact is large, the inspection is surely carried out without being affected by precision in positioning the electrode patterns. In other words, when an electrode is shifted from a proper position, inspection can be accurately executed without use of a high-precision positioning device, since the earth terminal and common electrode are surely in contact with each other. Further, if the common electrode does not have a sufficient width, inspection is still possible. Therefore, restriction on the layout of the electrode patterns is minimized, thereby increasing the degree of freedom in layout.
Furthermore, since the area in which the earth terminal and the common electrode are brought into contact with each other is large, a contact resistance upon the scan by the earth terminal on the common electrode can be made to remain at a minimum degree. This provides speedier and more stable inspection.
To achieve the aforementioned object, an electrode pattern inspection method of the present invention is characterized by comprising the steps of (a) earthing a common electrode connecting ends on one side of a plurality of electrodes with each other, (b) applying constant current to an electrode to be inspected among the plurality of electrodes so as to detect variation in a voltage generated by the constant current, and (c) measuring a voltage at an electrode adjacent to the electrode to be inspected so as to detect variation in the voltage.
By the foregoing method, the common electrode is earthed, constant current is applied to an inspected electrode, and a voltage is measured at an electrode adjacent to the inspected electrode. In other words, by earthing the common electrode, the plurality of electrodes connected with each other via the common electrode can be electrically separated. Therefore, by measuring a voltage at an electrode adjacent to an inspected electrode upon application of current to the inspected electrode, whether or not the inspected electrode and the adjacent electrode are short-circuited can be inspected.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.